There is little prior art for processing of low-grade manganese and related ores. Although several methods have been proposed, there are no proven processes for treatment of manganese nodules or cobalt-manganese crusts.
Acid leaching methods that have been proposed require either very long reaction time or the use of high temperature and pressure. A sulfur dioxide leaching system has been mentioned, but the process produces a solution that is not amenable to subsequent recovery of metals by known methods.
High temperature pyrometallurgical methods are undesirable because of the expense of water removal prior to processing. This drying operation will be very expensive for manganese nodules and crusts, which often contain 30 to 40 weight percent moisture.
Those concerned with these and other problems recognize the need for an improved process for leaching of manganese oxide ores.